Enhancing signals in a two-way radio system

ABSTRACT

Embodiments of the present invention can be used to enhance signals in a peer-to-peer radio system, such as a two-way radio system. In one embodiment, the invention includes receiving a communications signal on a channel from a remote radio at a radio using a plurality of antenna elements, such as an antenna array. The received communications signal includes a squelch code. The radio detects the squelch code, and enhances the received communications signal using the squelch code.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention applies to the field of wireless communicationssystems and, in particular, to two-way radio communications usingsquelch codes.

2. Description of the Prior Art

Personal Radio Service (PRS) is the name applied by the FederalCommunications Commission Wireless Telecommunications Bureau to cover abroad array of two-way (or, walkie-talkie) type radio services. Includedunder the PRS moniker are radio services such as the so-called 218-219MHz service, the Citizens Band (CB) radio service, the Family RadioService (FRS), the General Mobile Radio Service (GMRS), the Low PowerRadio Service (LPRS), the Medical Implant Communications Service (MICS),the Radio Control Radio Service, and the Wireless Medical TelemetryService.

These “two-way” radios, sometimes referred to as walkie-talkies orhandie-talkies, generally broadcast directly from one communicationsdevice (typically a portable radio) to another, or they may use arepeater to amplify their signals. These devices generally use allocatedchannelized spectrum. These channels can be frequency bands around acentral carrier. For example, the spectrum allocated to FSR has beendivided into fourteen (14) channels from 462.5625 MHz through 462.7125MHz, and again from 467.5625 MHz through 467.7125 MHz, with each channeloccupying a 30 KHz frequency band (see, e.g., 47 CFR §95.627).

Since anyone can use the allocated channels at any time, when a radio istuned to a particular channel, a user can hear anyone who transmits onthat channel. Also, if two people transmit simultaneously on a givenchannel, the radio frequency (RF) signals interfere with one another,and the listeners will likely hear noise. Thus, a user has to listen tothe conversations of other parties with whom the user does not wish tocommunicate if these parties are using the same channel. Furthermore, ifthese other parties communicate simultaneously with the user, or withpeople the user wishes to communicate with, this will interfere with theusers ability to communicate.

To address the problem of listening to the conversations of strangers,some manufacturers of such two-way communication devices enable the useof squelch codes. Squelch is the phrase used for muting a speaker. Forexample, two-way radios generally squelch the speaker until a minimumsignal strength is detected, so that the radio is not constantly hummingwith background noise. By using squelch codes, the radio onlyun-squelches the speaker when it detects the squelch code. Examples ofsquelch codes are Continuous Tone Coded Squelch System (CTCSS)sub-audible tones which are out-of-band tones and Digital Coded Squelch(DCS) code words, which are digital squelch codes. Motorola'strademarked version of these squelch systems are called Private Line(PL)™ and Digital Private Line (PL)™ respectively.

As an example, FSR uses CTCSS to create “sub-channels.” Each userselects which CTCSS tone to use in conjunction with a selected RFchannel. The radio then blocks, i.e. squelches, any signal received thatdoes not include the selected CTCSS tone. Thus, if two users select aCTCSS tone not used by other parties, then the two users will only heartransmissions from each other. However, the use of squelch codes doesnot solve the problem of interference. Two users transmitting on thesame channel at the same time using different squelch codes will stillinterfere with one another, leaving the receiver unable to render thedesired content.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention can be used to enhance signals in apeer-to-peer radio system, such as a two-way radio system. In oneembodiment, the invention includes receiving a communications signal ona channel from a remote radio at a radio using a plurality of antennaelements, such as an antenna array. The received communications signalincludes a squelch code. The radio detects the squelch code, andenhances the received communications signal using the squelch code.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereference numerals refer to similar elements and in which:

FIG. 1 is a flow chart of a process for enhancing a receivedcommunications signal in accordance with an embodiment of the invention;

FIG. 2 is a simplified block diagram of a two-way radio on which anembodiment of the invention can be implemented; and

FIG. 3 is a simplified block diagram of a peer-to-peer communicationsenvironment in which embodiments of the invention can be practiced.

DETAILED DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, an enhanced FSR radio hasan antenna array of two or more antennas. The radio can use the CTCSStone or the DCS code word as a training signal to determine spatialprocessing parameters, such as receive weights, to null interfererstransmitting simultaneously on the same channel.

One embodiment of the present invention is now described with referenceto FIG. 1. In this example, the user of a two-way radio wishes tocommunicate with another party herein referred to as the desired party.The user of the two-way radio and the desired party agree on a channelto communicate on using their respective two-way radios. Furthermore,the user and the desired party agree on a sub-channel as marked by asquelch code. Both the selection of the channel and the squelch code canbe manual or automatic.

First, the user's two-way radio receives 102 a communications signalfrom the desired party. The two-way radio uses two or more antennas, sothe number of versions of the received signal equals the number ofantenna elements used for reception. The communications signal may havebeen transmitted by the radio used by the desired party, or by arepeater in the area. The received communications signal includes thesquelch code, since the user has agreed with the desired party on thesquelch code.

The user's two-way radio detects 104 the squelch code, for example, byscanning for a reference version of the scan code. In one embodiment,the squelch code is used for its traditional purpose, and upon detectingthe squelch code, the two-way radio un-squelches the speaker, since thatis what the squelch code is designed for.

Furthermore, the two-way radio uses the squelch code to enhance 106 thereceived communications signal. In one embodiment, the two-way radiouses the squelch code as a training signal to enhance the receivedsignal. A training signal, also known as a pilot signal or a trainingsequence, can be used for measuring channel parameters andcharacteristics, such as SNR (signal to noise ratio), SINR (signal tointerference and noise ratio), spatial parameters, timing, and frequencyoffset. It can also be used for calibration, or the calculation ofspatial processing parameters.

Thus, a training signal can be used to determine a spatial processingstrategy, such as receive spatial processing weights. Training signalsare useful because the received signal is known at the receiver and cantherefore be compared with a reference signal that corresponds to theknown sent signal. Since the user's two-way radio knows the squelchcode, it can use it as a training signal.

In one embodiment of the present invention, the two-way radio uses thesquelch code to determine a spatial processing strategy for combiningthe various versions of the signal as received through the variousantenna elements. According to one such strategy, the known squelch codeis used to determine a set of weights that generates a signal that mostclosely matches the known squelch code. In particular, the set ofweights can be generated such that the correlation of the weighted sumof the received squelch code with a locally generated version of thesquelch code is high. The set of weights can be complex valued weightsrepresenting a phase and amplitude adjustment to each version of thesignal received though the corresponding antenna element.

For example, if the squelch code is a CTCSS tone and the two-way radiohas two antenna elements, the two-way radio can adjust the relativephase and amplitude of signals from one antenna element to most closelymatch the CTCSS tone being received with the expected CTCSS tone. Thiscan be done by a feedback loop designed to match two tones. Similarly,if the two-way radio receives a DCS code word, it can adjust the phaseand amplitude of the versions of the signal to correlate the receivedDCS code word with the reference DCS code word selected by the user andthe desired party.

Spatially processing the received communications signal can enhance thequality of the received signal even in the absence of severeinterference. However, in the case of severe interference, such whenreceiving an interfering signal from an interfering party using the samechannel as the user and the desired party (also known as cross-talk),spatially processing the received signals can mitigate the interferencecaused by the interfering signal. In one embodiment, the interferingsignal is nulled so that the user hears only the signal sent by thedesired party.

Two-Way Radio Structure

FIG. 2 depicts an example component arrangement in a two-way radio 200.The two-way radio's 200 antenna elements 202 are connected to a duplexer204 to permit the antenna elements 202 to be used for both transmissionand reception. The dots between the antenna elements 202 symbolize thatany number of antenna element greater than one can be used. Usually, inhandie-talkie devices the duplexer 204 is controlled by a push-button.In one embodiment, when this push-button is activated the duplexer 204is in transmit mode, otherwise the duplexer 204 is in receive mode. Theduplexer outputs serves as inputs to receivers 206. The receivers 206can perform down-converting, demodulation, analog-to-digital conversion,or other reception related tasks depending on implementation. Forexample, an analog FSR radio will not need analog-to-digital conversion.

The receiver signals serve as input for the combiner module. In oneembodiment, the combiner module adjusts the phase and amplitude of thereceiver signals using a set of receive weights determined by trainingon the squelch code. In one analog embodiment, the combiner module 208can be implemented as a feedback circuit well known in the art thatmatches the expected squelch code, such as a CTCSS tone, and adjusts andcombines the receiver signals accordingly. In one digital embodiment,the combiner module 208 can be implemented as a processor, such as aMotorola DSP56300 Family Digital Signal Processor, that correlates thereceived symbols with the expected digital squelch code, such as a DCScode word, to determine receive weights. The calculation of receiveweights is described, for example, in U.S. Pat. No. 5,828,658, issuedOct. 27, 1998 to Ottersten et al. and U.S. Pat. No. 5,642,353, issuedJun. 24, 1997 to Roy, III et al.

The signal produced by the combiner module 208 is input for theInput/Output Module 210. In one embodiment, the Input/Output Module 210controls Audio I/O 212, such as a microphone for audio input and aspeaker for audio output. The Input/Output module 210 can furtheroperate a Channel Selector 214 used by a user to select the channel,such as one of the fourteen FSR frequency bands, for communication witha desired party. The Input/Output Module 210 can also operate a SquelchCode Selector 214 used by the user to select the squelch code used bythe desired party. The Squelch Code Selector 214 can be implemented, forexample, as a CTCSS selector or a DCS selector. In one embodiment, theSquelch Code Selector 214 can allow for both manual and automatedselection of a squelch code. The Input/Output Module 210 can operateother i/o devices, such as displays, keyboards, and various knobs andbuttons, such as the duplexer button discussed above.

The two-way radio 200 also includes a transmitter 212 for transmittingsignals through one or more of the antenna elements 202. In oneembodiment, only one antenna is used for omni-directional transmission,and thus only one transmitter 212 is needed. However, other embodimentscan use multiple antenna elements 202 and multiple transmitters 212 totransmit in a directional manner. In one such embodiment, thetransmitter is also coupled to the Combiner Module 208 that candetermine and apply transmit weights to the signal to be transmitted. Inone embodiment, the signal to be transmitted is voice from a microphone,and the transmitter 212 performs modulation and up-conversion. In analternate embodiment, the signal is digitized voice data, and thetransmitter 212 also performs digital to analog conversion.

In one embodiment, the two-way radio 200 also includes a Squelch Module214. The Squelch Module 214 is pictured as a separate module, but can beimplemented as part of the Combiner Module 208. The Squelch Module 214detects the squelch code selected using the Squelch Code Selector 216and un-squelches the Audio I/O 212, e.g. a speaker, in response.

Demonstrative Example

FIG. 3 is a block diagram of an example operating environment withinwhich example embodiments of the present invention may be practiced. Asdepicted in FIG. 3, a personal radio services (PRS) communicationenvironment 300 is depicted as including wireless communication devices301-305. PRS devices 301-303 are labeled as Enhanced PRS (EPRS)communication devices to show that an embodiment of the presentinvention is implemented in these devices. The PRS communicationsenvironment 300 also includes legacy PRS units 304 and 305. Inaccordance with the illustrated example embodiment, EPRS 303 and PRS 305are each broadcasting on a user-selected communication channel andsquelch code. According to the illustrated example embodiment, each ofthe transmitting devices 303 and 305 are broadcasting on the samecommunication channel, channel 3, denoted as signals 312 and 314,respectively. In this regard, conventional PRS communication devices,e.g., PRS device 304, will not receive either of the broadcast signals312 or 314 as simultaneous communication over the same communicationchannel generates too much interference from which the conventional PRSdevice 304 is often unable to recover a usable signal.

In contrast, an EPRS device 301 operating in the same environment andtuned to the communication channel and using the appropriate squelchcode (e.g., Ch. 3, squelch code 22) will still receive and render thesignal of interest 312 using spatial processing. The architecture of theEPRS can be fully compatible with legacy PRS communication devices. Thatis, since the spatial processing is carried out in the receiver, an EPRScommunications device will operate as described above regardless ofwhether the transmitting device is an EPRS device or a conventional PRSdevice. Such compatibility with legacy PRS devices is particularlyillustrated with reference to EPRS 302 and PRS 305 in FIG. 3.

General Matters

In the description above, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout some of these specific details. In other instances, well-knownstructures and devices are shown in block diagram form.

The present invention includes various steps. The steps of the presentinvention may be performed by hardware components, such as those shownin FIG. 2, or may be embodied in machine-executable instructions, whichmay be used to cause a general-purpose or special-purpose processor orlogic circuits programmed with the instructions to perform the steps.Alternatively, the steps may be performed by a combination of hardwareand software. The present invention is described in the context of apeer-to-peer wireless network of two-way radios, such as FSR. However,the present invention may be implemented in other networks, and inpeer-to-peer networks that also use repeaters, such as GMRS. Thesetwo-way radios may be implemented in various devices, such ashandie-talkies, cellular phones, PDA's, laptop computers, or any otherwireless devices. Generally, since these devices use radio waves, theymay be generally referred to as radios.

Embodiments of the present invention may be provided as a computerprogram product, which may include a machine-readable medium havingstored thereon instructions, which may be used to program a computer (orother electronic devices) to perform a process according to the presentinvention. The machine-readable medium may include, but is not limitedto, floppy diskettes, optical disks, CD-ROMs, and magneto-optical disks,ROMs, RAMs, EPROMs, EEPROMs, magnet or optical cards, flash memory, orother type of media/machine-readable medium suitable for storingelectronic instructions. Moreover, the present invention may also bedownloaded as a computer program product, wherein the program may betransferred from a remote computer to a requesting computer by way ofdata signals embodied in a carrier wave or other propagation medium viaa communication link (e.g., a modem or network connection).

Many of the methods and apparatuses are described in their most basicform, but steps or components can be added to or deleted from any of themethods and apparatuses without departing from the basic scope of thepresent invention. It will be apparent to those skilled in the art thatmany further modifications and adaptations can be made. The particularembodiments are not provided to limit the invention but to illustrateit. The scope of the present invention is not to be determined by thespecific examples provided above but only by the claims below.

It should also be appreciated that reference throughout thisspecification to “one embodiment” or “an embodiment” means that aparticular feature may be included in the practice of the invention.Similarly, it should be appreciated that in the foregoing description ofexemplary embodiments of the invention, various features of theinvention are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment of this invention.

1-38. (canceled)
 39. A method adapted for use in a receiver including aplurality of antenna elements, wherein the receiver is adapted toreceive a first signal, the method comprising: detecting a squelch codein said first signal; and enhancing a response of the receiver to saidfirst signal in response to at least the squelch code by substantiallynulling an interfering signal appearing on a same channel as the firstsignal.
 40. The method of claim 39, wherein said substantially nullingthe interfering signal comprises spatial processing by determining a setof spatial processing weights using the squelch code and combining thefirst signal received by the plurality of antenna elements according tothe set of spatial processing weights to provide a combined signalrelated to the first signal.
 41. The method of claim 39, wherein squelchcode comprises a Continuous Tone Coded Squelch System (CTCSS)sub-audible tone.
 42. The method of claim 39, wherein the squelch codecomprises a Digital Coded Squelch (DCS) code word.
 43. The method ofclaim 39, wherein the receiver is compatible with a Personal RadioService.
 44. The method of claim 43, wherein the Personal Radio Serviceis selected from a group consisting of 218-219 MHz service, a CitizensBand service, a Family Radio Service, a General Mobile Radio Service, aLow Power Radio Service, a Medical Implant Communications Service, and aWireless Medical Telemetry Service.
 45. A machine readable medium havingstored thereon data representing instructions that, when executed by aprocessor of a receiver including a plurality of antenna elementswherein the receiver is adapted to receive a first signal, cause theprocessor to perform operations comprising: detecting a squelch code insaid first signal; and enhancing a response of the receiver to saidfirst signal in response to at least the squelch code by substantiallynulling an interfering signal appearing on a same channel as the firstsignal.
 46. The machine readable medium of claim 45, wherein theinstructions further cause the processor to perform said substantiallynulling the interfering signal by spatial processing to determine a setof spatial processing weights using the squelch code and to combine thefirst signal received by the plurality of antenna elements according tothe set of spatial processing weights to provide a combined signalrelated to the first signal.
 47. The machine readable medium of claim45, wherein squelch code comprises a Continuous Tone Coded SquelchSystem (CTCSS) sub-audible tone.
 48. The machine readable medium ofclaim 45, wherein the squelch code comprises a Digital Coded Squelch(DCS) code word.
 49. The machine readable medium of claim 45, whereinthe receiver is compatible with a Personal Radio Service.
 50. Themachine readable medium of claim 49, wherein the Personal Radio Serviceis selected from a group consisting of 218-219 MHz service, a CitizensBand service, a Family Radio Service, a General Mobile Radio Service, aLow Power Radio Service, a Medical Implant Communications Service, and aWireless Medical Telemetry Service.
 51. A system comprising: a pluralityof radios capable of two-way communications, at least a first radioincluding a plurality of antenna elements, said at least first receiverincluding: means for detecting a squelch code in a first signal; andmeans for enhancing a response of the at least first radio to said firstsignal in response to at least the squelch code by substantially nullingan interfering signal appearing on a same channel as the first signal.52. The system of claim 51, wherein said means for enhancing furthercomprises spatial processing means adapted to determine a set of spatialprocessing weights using the squelch code and adapted to combine thefirst signal received by the plurality of antenna elements according tothe set of spatial processing weights to provide a combined signalrelated to the first signal.
 53. The system of claim 51, wherein squelchcode comprises a Continuous Tone Coded Squelch System (CTCSS)sub-audible tone.
 54. The system of claim 51, wherein the squelch codecomprises a Digital Coded Squelch (DCS) code word.
 55. The system ofclaim 51, wherein the receiver is compatible with a Personal RadioService.
 56. The system of claim 55, wherein the Personal Radio Serviceis selected from a group consisting of 218-219 MHz service, a CitizensBand service, a Family Radio Service, a General Mobile Radio Service, aLow Power Radio Service, a Medical Implant Communications Service, and aWireless Medical Telemetry Service.